This application claims benefit to U.S. provisional application Ser. No. 60/132,823, filed May 6, 1999.
1. Field of the Invention
The present invention relates generally to the field of mobile communications. More particularly, the present invention relates to a system and method for sharing one analog-to-digital converter (ADC) between a keypad and touch panel.
2. Related Art
Many mobile communications devices are now combining wireless phone technology with hand-held computer platforms that provide personal information management. Such hand-held computer devices are called personal digital assistants (PDAs). Combination mobile communications devices usually operate as two separate instruments, requiring separate liquid crystal displays (LCDs) and additional circuitry to read the separate input devices of the wireless phone and the PDA.
Matrix encoded keyboards and keypads are used extensively as input devices for computers and telephones. Such keyboards and keypads are usually mounted on a flex circuit and require multiple signals to detect which key is pressed. For example, a 4 by 4 matrix keypad, which contains sixteen input keys, requires eight signals. When the keyboard or keypad is implemented on a flip cover, as may be the case with a wireless phone or PDA, multiple signals are routed to the body of the communications device through a hinge. The routing of multiple signals through a hinge causes the instrument to be less durable and may lead to the breakage of the hinge if the instrument is constantly picked up by grasping the flip cover.
Many PDAs require a two-channel analog-to-digital converter (ADC) to read the touch panel. When the PDA is combined with a wireless telephone that implements the keypad on a flip cover, additional circuitry usually includes an additional ADC to read the keypad on the flip cover and an additional LCD for the wireless telephone display.
What is needed is an efficient and cost effective way to integrate a PDA and wireless telephone with a flip cover that is lightweight, durable, and easy to operate.
What is further needed is the integration of a PDA and wireless telephone that work together by allowing the keypad and touch panel to share one ADC.
The present invention satisfies the above mentioned needs by providing a communications device that efficiently integrates a flip telephone with a personal digital assistant (PDA). The present invention operates as a single unit by sharing an ADC between a keypad and a touch panel. According to the present invention, a keypad that produces a voltage level indicative of a key pressed and a touch panel that produces a voltage level indicative of a location on the touch panel that has been pressed are both coupled to the input of an analog-to-digital converter (ADC). A processor, coupled to the output of the ADC, reads the ADC output.
An advantage of the present invention is cost. Only one ADC is needed. Also, the same software that reads the touch panel can be used to read the keyboard.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.